“Matched/Mismatched” Diastereomeric Dirhodium(II) Carboxamidate Catalyst Pairs. Structure−Selectivity Correlations in Diazo Decomposition and Hetero-Diels−Alder Reactions

Homo-ligated dirhodium(II) carboxamidates provide well-defined structural frameworks with which
to investigate catalyst-controlled multiple asymmetric induction (“match/mismatch” effects).
Diastereomeric pairs of methyl 2-oxoimidazolidine-4(S)-carboxylate ligands containing 2-phenylcyclopropane (4S,2‘S,3‘S-HMCPIM and 4S,2‘R,3‘R-HMCPIM) and N-benzenesulfonylproline (4S,2‘S-HBSPIM and 4S,2‘R-HBSPIM) attachments at the 1-N-acyl site have been prepared; the resulting
(cis-2,2)-Rh2L4 compounds have been produced in good yields, and the X-ray crystal structure of
each dirhodium(II) compound has been obtained. The incorporation of additional stereocenters into
the dirhodium(II) ligands leads to recognizable levels of double asymmetric induction for C−H
insertion, cyclopropanation, and hetero-Diels−Alder cycloaddition applications. The configurationally
“matched” cases provide modest increases in enantioselectivity for intramolecular C−H insertion
reactions relative to the model catalyst Rh2(MPPIM)4, but applications of the configurationally
mismatched catalysts result in significant lowering of enantioselectivity. The Rh2(BSPIM)4 catalysts
show the highest degree of differential selectivity. Hetero-Diels−Alder reactions show inverse
behavior from the configurationally matched and mismatched Rh2L4 catalysts to that found in the
metal carbene transformations.